Microstructure and properties of heavily deformed Cu-Ag-Ce in situ nano-filamentary composite

Abstract: The microstructure and properties of heavily deformed Cu-Ag-Ce in situ nano-filamentary composite were studied in this paper. As cast, copper matrixes were dendritic and Ag-rich phases, some of which present spheroidizing tendency, were embedded in Cu dentritic arms. After heavily deforming, Ag-rich phases develop into fibers: the thick fibers with a size of more than 50 nm and the thin ones with a size of less than 30 nm. Strengthening of Cu-Ag-Ce in situ nano-filamentary composite could be divided into two stages and the combination of different strength and conductivity could be obtained through controlling reducing area, intermediate heat treatment and stabilizing treatment. The results revealed that heavily deformed Cu-Ag-Ce in situ nano-filamentary composite had high strength ( >1.5GPa) and high conductivity(>65%IACS).

Biocompatibility evaluation of NiTi SMA stent via intervenient therapy

NiTi shape memory alloy (SMA) stent with film are the long-term implanted medical devices which could be used in human’s organ, such as esophagus, bile duct, urethra-prostate and blood vessel, by intervene therapy. It is very important to have a good biocompatibility for implanted device. According to standard ISO 10993, we completed biocompatibility evaluation of NiTi stent that included following tests: cytotoxicity, sensitization, genotoxicity, hemolysis and acute systemic toxicity. The results of tests qualify the NiTi stent, and provide an optimistic conclusion for the eventual use of NiTi stent as implanted medical devices.

Preparation and Electrochemical Properties of Porous Platinum Electrode

Porous platinum electrodes were prepared by adding YSZ,as an active material,in platinum paste.Relationship between microstructure and electrochemical performance of O 2(g),Pt/YSZ electrode have been characterized by SEM and cyclic voltammetry.Results showed that the microstructure of platinum electrode is a significant impact on the cyclic voltammetry.With the increase of platinum electrode's porosity,the area of three-phase boundary of O 2(g) /Pt/YSZ was increased.The electrochemical reactivity was also enhanced.These were presented as the increase of current density and cathode voltage in cyclic voltammetry.

Preparation and Properties of AlSi1Cu0.5 Alloy

The microstructure of casting AlSi1Cu0.5 alloy was investigated as well as the microstructure and the properties of AlSi1Cu0.5 alloy treated by deformed processing and heat treatment. The results of experiments demonstrate that casting AlSi1Cu0.5 alloy is inhomogeneous and the microstructure is dendritic; by deformed processing and heat treatment, the distribution of Si and Cu elements is improved and the grain size is below 100 μm.

Retrogression characteristics of a novel Al-Cu-Li-X alloy

Retrogression characteristics of a novel Al-Cu-Li-X alloy of 2A97 were studied by hardness testing, transmission electron microscopy （TEM）, and differential scanning calorimetry （DSC）. The retrogression treatments of aging at 155°C for 12 h followed by aging at 220 and 240°C were chosen by determining the peak temperature of δ＇ precipitation at 230°C by DSC. The retrogression treatment at a lower temperature of 220°C causes the precipitation and coarsening of δ＇ and θ＇ phases in the matrix, resulting in an increase in hardness. Retrogression at a higher temperature of 240°C causes the dissolution and coarsening of δ＇ and θ＇ precipitates in the matrix and on the grain boundaries, resulting in a decrease in hardness. Microstructural changes upon retrogression including the appearance of equilibrium precipitates such as T1, T2, δ＇, and θ are confirmed by the selected area electron diffraction and the bright and dark field image analysis.

Characterization of phases in Mg-10Y-5Gd-2Zn-0.5Zr alloy processed by heat treatment

Characterizations of phases in Mg-10%Y-5%Gd-2%Zn-0.5%Zr （WGZ1052） alloy during heat treatments were investigated by OM, XRD, SEM and EDS. The mechanisms of microstrucmre evolution were discussed. The results show that, after high temperature heat treatments, the Mg12ZnY phases still exist. During solution-treatment at 535 ~C, the amount of the long-period stacking order structures decreases. At 545℃ for 20 h and 24 h, there are still remnant Mg12ZnY compounds in the Mg matrix, the shape of which does not change and the amount does not decrease obviously.

Relationship between mechanical property and microstructure of NiTi shape memory alloy

The relationship between mechanical property and microstructure of NiTi shape memory alloy has been studied. It was founded that with increasing prestrain the memory recovery rate decreased, but the recovery stress and the recovery strain increased first and then decreased. The recovery stress and the recovery strain reached maximum at about 11% prestrain. The TEM(Transmission Electron Microscope) results of the alloy indicated that the microstructures with different prestrain of the alloy had obvious characters. At 9% prestrain, the martensite anamorphosis of the alloy still presented self-cooperation configuration, and some martensites have become thick obviously because of tropism. When the prestrain was 11%, the martensite anamorphosis has become completely thick and tropism became consistent. As the prestrain increased to 13%, the microstructures of the alloy have become disordered, the tropism became inconsistent and the interface became blurry.

Effect of temperature on nitinol electropolishing

Electropolishing has been used in TiNi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. In this paper, effect of temperature on nitinol electropolishing is explored. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following a near Gauss law. The relationship between the temperature and surface roughness follows near parabolic law, the relationship between the temperature and surface reflectivity follows near Sigmoidal law.

A new type of inferior vena cava filter and its animal experiment

This article explains the definition of pulmonary embolism as well as its causes and elaborates on a new type of inferior vena cava filter(VCF)we have developed. Shaped like a waistdrum, the VCF is mainly made of TiNi shape memory alloy-wire. It has a subulate wire frame which can intercept the thrombus on each side. Its medial body is made up of straight shape memory alloy-wire . Every pillar is bound by several shape memory alloy springs. This type of inferior vena cava filter has a good resistance to fatigue and is hard to be broken. Through animal experiments its framework has been proved to be lasting. Neither deformation nor fragmentation happened when the VCF had been kept in the body for a long time. The thrombus interception efficiency of our VCF is higher than imported VCFs. The filter is unfavorable for thrombosis. After implantation, the IVC was completely unimpeded and no displacement occurred. Moreover the VCF did little damage to the Wall of vein. Neither IVC perforation nor haematoma occurred after the operation.

Correlation between pass-through flux of cobalt target and microstructure and magnetic properties of sputtered thin films

Cobalt thin films were deposited on silicon substrates by magnetron sputtering two commercial cobalt targets with different pass-through fluxes(PTFs).The influences of PTF on the magnetic properties of sputtered thin films were investigated.The results indicate that under the same sputtering conditions,cobalt thin film deposited by Co target with high PTF(84.21%) has lower remanence ratio(0.65),while cobalt thin film prepared by Co target with low PTF(69.13%) has higher remanence ratio(0.87).Through introducing an external magnetic field parallel to the film surface during sputtering processes,both the remanence ratios of cobalt thin films prepared by the two targets can be enhanced to approach 1.High-resolution transmission electron microscopy(HRTEM) images show that in the absence of the external magnetic field during sputtering,cobalt thin film deposited by the target with high PTF is randomly oriented in crystallographic orientations,which is due to that Co atoms have no enough time to migrate and diffuse on substrate and the atomic stacking is disordered.It is worth mentioning that crystallographic orientations of cobalt thin film deposited by target with low PTF are relatively consistent,resulting in relatively higher remanence ratio.In addition,HRTEM analysis indicates that the external magnetic field during sputtering drives the Co grains to arrange in a regular order with(002) orientation,leading to the improvement in remanence ratios.

Novel twinned Al3Sc dendrites in as-casted Al-Sc alloy

Al-Sc alloys with high Sc contents are served as sputtering targets for making high-performance piezoelectric devices.The micro structure of these alloys would affect the sputtering process and the final quality of the functional devices.In this study,the microstructure in as-c as ted Al-20%Sc(in atomic ratio)alloys is characterized and the feathery Al3Sc grains with twin relationships are reported for the first time.The crystallographic features of twined structures and growth directions are quantitatively analyzed by electron backscatter diffraction(EBSD)technique.

AlScN films prepared by alloy targets and SAW device characteristics

In this paper,we reported a surface acoustic wave(SAW)device prepared and optimized by piezoelectric films containing AIN,AIScN(Sc-20 at%)and AIScN(Sc-30 at%)by reactive magnetron sputtering using Al and AISc alloy targets.We calculated the material intrinsic electromechanical coupling coefficient k_(t)^(2) of AlScN(Sc-20 at%)and AlScN(Sc-30 at%)which are much better than AIN.It can be explained by the lattice softening.Furtherly,the results were confirmed by transmission electron microscopy(TEM)observation of the microstructure.Then the SAW devices based on three thin films were tested by vector network analysis obtaining the device equivalent electro mechanical coupling coefficient k_(eff)^(2).The value of AIScN(Sc-20 at%)k_(eff)^(2),which equals to 1.94%,is higher than that of AIN and AIScN(Sc-30 at%)while the value of AIScN(Sc-30 at%)k_(t)^(2) is higher than that of others.It is shown in our study that the crystallinity and orientation of the material still have a greater impact on k_(eff)^(2) but it does not have influence on k_(t)^(2) in the actual device preparation process.

In situ atomic-scale observation of dislocation behaviors in twin-structured Pt nanocrystals

The deformation mechanisms of twin-structured metallic materials have attracted great interest.Though previous theoretical predictions have suggested that the repulsive force of the twin boundary(TB)can significantly affect the deformation of twinstructured metals,it remains unclear whether this prediction applies to experimental conditions.In this paper,the atomic-scaled deformation process of twin-structured Pt nanocrystals was in situ observed using our home-made device in a high-resolution transmission electron microscope.We have shown that the plastic deformation of the twin-structured Pt nanocrystals was governed by full dislocation generation as well as Lomer dislocation(LD)lock formation and destruction.After LD locks were destructed,these full dislocations tended to move towards the surface of the nanocrystals.The findings revealed that due to the ultra-high repulsive force of TB on dislocation,there was no dislocation-TB reaction during the deformation.These findings can enrich our understanding of the dislocation behaviors of twin-structured nanocrystals.

Application of the O-line model to martensite crystallography

The O-line model is usually applied to precipitation crystallography.Its application to investigation of martensite crystallography has received little attention.In this paper,the relationship between O-line model and the prism matching model for martensite crystallography is established.The formulas in the O-line model are applicable to martensite crystallography.Analytical solution of the habit plane corresponding to the minimum shape strain has been derived.A calculation example of {3 10 15}f martensite in a ferrous alloy is provided.While the results are in agreement with the former models for martensite crystallography,the advantage of O-line model is that it offers analytical solutions,facilitating further systematic investigations.